Insulator-to-Metal Crossover near the Edge of the Superconducting Dome in Nd$_{1-x}$Sr$_x$NiO$_2$

TL;DR

This study reveals a crossover from metallic to insulating behavior in Nd$_{1-x}$Sr$_x$NiO$_2$ thin films near the superconducting dome, highlighting strong correlations and an anomalous insulating state.

Contribution

It provides the first systematic magnetotransport analysis of Nd$_{1-x}$Sr$_x$NiO$_2$ films, identifying a crossover in resistivity behavior and characterizing the nature of the insulating state.

Findings

Resistivity shows a crossover from T^2 to log(1/T) behavior with doping.

The insulating behavior is robust against magnetic fields, indicating strong correlations.

No evidence of non-Fermi-liquid behavior near the quantum critical point.

Abstract

We report a systematic magnetotransport study of superconducting infinite-layer nickelate thin films Nd$_{1-x}$Sr$_x$NiO$_2$ with $0.15 \leq x \leq 0.225$. By suppressing superconductivity with out-of-plane magnetic fields up to 37.5 T, we find that the normal state resistivity of Nd$_{1-x}$Sr$_x$NiO$_2$ is characterized by a crossover from a metallic $T^2$-behavior to an insulating log(1/$T$)-behavior for all $x$ except $x = 0.225$, at which the resistivity is predominantly metallic. The log(1/$T$)-behavior is found to be robust against magnetic fields, inconsistent with scenarios involving localization or Kondo scattering, and points to an anomalous insulating state possibly driven by strong correlations. In the metallic state, we find no evidence for non-Fermi-liquid behavior arising from proximity to a putative quantum critical point located inside the superconducting dome.